The present invention concerns an improved strap controlling the motion of weft yarn grippers in shuttleless looms.
It is known that the straps--usually having a composite structure based on plastic material reinforced with various types of fibers--which control the motion of weft yarn grippers in looms undergo rather fast wear, owing to the strong stresses to which they are subjected due to their function. The straps wear on the sides and on the upper and lower surfaces; above all, it is the lateral areas of the upper surface, more frequently stressed, which get worn due to the bending movements of the straps. Since these movements, as well as the stresses and wear of the straps depend on the highly variable accelerations which the straps, undergo in their motion, the wear is very uneven both transversally to the straps and longitudinally thereto.
Due to wear, the straps have to be replaced fairly frequently, and obviously before wearing to the extent of possibly breaking, which would be seriously prejudicial to the proper performance of the loom and to the actual safety of the operators. This requires frequent undesired checks, which are a waste of time for the operators and limit the loom productivity. In fact, these checks cannot be carried out immediately and need to be thorough, particularly in correspondence of the bottom surface of the strap which bears on the lower warp web in the shed.